Display document type in document filter
Rename .document-filter-page to .documents-index
Remove duplicate documents-index layout CSS
Fix tests checking for filter result summaries

Looks like id was changed to class at some point and tests
weren't updated.
Move filter helper to documents-index view CSS

These styles are only used on the documents-index.
Remove unnecessary feed class
Add line to policies filter summary
Add comma to number of filter results
Add tests for JS filter pluralising